Shell moderately large, 19-53 mm., very similar to Gemmula, with its gemmate peripheral carina and tall narrowly conical protoconch of four axially costate whorls but with a shorter more twisted anterior canal, and a different sinus, which is a broadly open V, U- shaped at its apex, not a narrow slit, as in Gemmula. Radula, according to Thiele (P. bisinuata), with, in addition to "wishbone"-type marginals, a large unicuspid rectangular based central. A feature of the genus is a spout-like labial projection originating from a basal subcarina. This, however, is not a constant feature, even within a species, and is comparable with the condition of multiple flutings of the outer lip, in some species of Gemmula.

Range — Recent, the deep ocean basins of the Indian Ocean, Natal, East Africa and the East Indies, the North Atlantic, off Bermuda, 1700 fathoms, and the Pliocene of Timor.

Shell resembling Gemmula s.s., but anal sinus typically widely open, siphonal rostrum shorter.

Notes: Practically all modern authors accept Ptychosyrinx as a full genus. However, I agree with Shuto (1961) that essential resemblances to Gemmula are too great. Although Powell (1964) and Oyama (1966) separated Ptychosyrinx by its large rachidian plates (as illustrated by Thiele 1929: Fig. 436), similar plates are now known to occur in many Gemmula species. (On the other hand, Barnard (1958) reported rachidians to be absent in Ptychosyrinx lobata; however, their absence needs confirmation as he used unstained radula preparations and may conceivably have overlooked these plates.) The openly V-shaped anal sinus, also regarded by Powell and Oyama as diagnostic, is a doubtful character. Thus the type figure of Ptychosyrinx timorensis teschi Powell (1964: pl. 223, Fig. 5) shows a sinus typical for Gemmula, yet on the other hand Gemmula microscelida (Dall, 1895) has a Ptychosyrinx-style sinus. Moreover, individual variation within species of Gemmula often offers intermediate character-states. The basal lip sinus, sometimes believed to be diagnostic of Ptychosyrinx, has been shown to be an occasional malformation that may also occur in Gemmula. The concentric operculum reported by Thiele (1925) for the type species, was probably the result of damage and subsequent repair. The protoconch (Thiele 1925: pl. 23, Fig. 4) resembles that of Gemmula. I have retained Ptychosyrinx as a subgenus but have considerable doubt that its validity can be maintained.